Recently, as a small electronic equipment such as a cellular phone or a portable communication terminal is widely used, a surface-mount-type package capable of soldering an electrode-lead directly with a substrate has become popular in a semiconductor device of a resin-sealed type.
Conventionally, it is well known to mount a semiconductor chic on an upper surface of an electrode-lead to which an Au film, a Ni film, and a Au film are stacked in order. The semiconductor chip is connected to another electrode-lead. The electrode-leads and the semiconductor chip are housed in a package molded out of a resin. A lower surface of the electrode lead is exposed at a surface of the package.
However, in this semiconductor device, there is a problem in that radiation performance of a heat generated in the semiconductor chip is poor because thermal conductivity of Ni of the electrode-lead is low.
A printed wiring board having a Cu film, a Ni film and an Au film stacked on a board is proposed in Japanese Patent Application (Koukai) No. 2002-359459 (Corresponding to U.S. Patent Application (published) No. US2002/0179328A1). In this printed wiring board, the Ni plating film is formed on a surface of the Cu foil which has a wiring pattern, and the Au plating film is formed on a surface of the Ni plating film.
Another printed wiring board is proposed in Japanese Patent Application (Koukai) No. 2001-251041. In this printed wiring board, a Cu plating film which has a wiring pattern is formed on both surfaces of an electric insulating board. A Ni plating film is formed on the Cu plating film. An Au plating film is formed on the Ni plating film.
However, the above-mentioned printed wiring boards are directed to boards to mount electronic parts housed in a package, for instance, and the references do not disclose a way to house the semiconductor chip in the package of the surface mount type.